Safe wafer pick-and-place is a very important technical indicator for integrated circuit production lines. Generally, the breakage rate of wafers due to wafer handling equipment in the course of production should be less than 0.001%. Compared with a single-wafer processing system, a batch-type wafer heat treatment system requires more wafer transfer and pick-and-place operations in each production process, which makes higher demands of safe and reliable wafer transfer and pick-and-place.
Nowadays, robots have been widely applied in the field of semiconductor IC manufacturing technology and have become important tools in wafer handling systems for picking, placing and transferring unprocessed and processed wafers. The robot can response to instructions to accurate move to a point of wafer location in a three-dimensional or two-dimensional space to pick and place wafers.
Currently, the positional parameters of the robot during handling a wafer in the batch-type wafer heat treatment equipment are generally obtained by offline teaching. The offline teaching data of the positional parameters are usually stored in a memory and calibrated periodically. The robot performs the pick-and-place operation to the wafers located in a wafer carrier according to the stored offline teaching data. However, factors such as environment temperature variation, load variation, and mechanical deformation of the wafer carrier may cause collision of the robot with the wafer or the wafer carrier when the robot performs the pick-and-place operation to the wafer at a stored position on the offline basis, resulting in irreparable losses such as damages to the wafer or equipment. In addition, thermal deformation of the wafer during the heat treatment may also cause an offset between an actual location of the wafer and the robot positional parameter of the offline teaching data, which puts the robot pick-and-place operation in an unsafe condition.
FIG. 1 is a structural view illustrating the positions of the robot in the conventional wafer transfer and pick—and place process. If a wafer 2 positioned on a supporter 3 is in an abnormal condition such as in an inclined state, the robot 1 may perform the pick-and-place operation to the wafer 2 under an unsafe condition, and damages to the wafer 2 and the equipment (including the robot 1) can be easily occurred.
Accordingly, after the place operation or before the pick-up operation, an accurate pose recognition for the wafers 2 on the supporter 3 is required, such that proper measures can be taken to the wafers in the abnormal condition to ensure a safe pick-and-place operation.